What is the function of the PEN conductor in a TN-C-S system, and where is it separated into PE and N?

• A. PEN is the protective conductor only; separation occurs at the main fuse.
• B. PEN is a dedicated earth conductor; separation occurs at the socket.
• C. PEN is the neutral only; separation occurs at the transformer.
• D. PEN provides combined protective earth and neutral; it is separated into PE and N at the main distribution board or within the installation.

Answer: (D)

In a TN-C-S system, a single conductor called PEN carries both protective earth and neutral from the supply to the installation. It provides both functions up to the point where the building’s wiring splits into separate protective earth (PE) and neutral (N) conductors. The separation normally happens at the main distribution board or at the service entry within the installation. After this point, PE provides the earth path for protective bonding, and N serves as the neutral conductor for circuits. This is why the option stating that PEN provides combined protective earth and neutral and is separated into PE and N at the main distribution board or within the installation is correct.